Pointing device

ABSTRACT

An electronic pointing cursor control device such as a trackball or mouse, comprising a first chamber adjoined to a second chamber, the chambers being separated by a fluid-tight wall comprising an optically permeable region; wherein the first chamber contains electronic components including optical detectors directed towards the optically permeable region and a ball protruding through an aperture provided in the second chamber, the detectors being operable in use to detect and generate electronic signals representative of motion of the ball. Also provided is an electronic pointing or cursor control device comprising a ball and optical detectors operable to detect and generate electronic signals representative of motion of the ball, wherein the detectors are mounted such that a radial line from the ball to the detectors forms a non-zero angle with a diametric line though the ball normal to the mounting plane of the device.

This invention relates to electronic pointing devices for use with apersonal computer or other computer controlled electronic equipment. Theterm ‘pointing device’ should be interpreted broadly, to cover both miceand trackballs (also sometimes known as trackerballs). Such devices aretypically used to control the movement of a cursor on a display screen.

Pointing devices or cursor control devices such as mice and trackballsare commonplace wherever there are computers or computer controlledequipment.

A pointing device is generally vulnerable to the ingress of liquid,which can cause potentially fatal damage to its internal circuitry andlead to failure of the device. In many cases, the environment in whichthe pointing device is situated greatly increases the risk of liquidingress. Trackballs are often used in industrial locations such asfactories, in which there may be an enhanced risk of liquid spillage. Insome applications liquid ingress is virtually inevitable. For example,trackballs may be used to control ultrasound equipment in hospitals,where there is a high likelihood of ultrasound gel getting into thetrackball mechanism. The term liquid as used herein should be taken toinclude gels, oils and other common fluids. Mice are also often prone toliquid ingress, which may result from accidents such as the spillage ofa drink in an office. In outdoor applications, pointing devices arehighly susceptible to the ingress of rainwater and other forms ofprecipitation.

If liquid is accidentally taken in by a pointing device, then this canalso affect electrical or electronic apparatus connected or installedwith it. In such cases the pointing device, and often the associatedapparatus too, must immediately be switched off, either to replace thepointing device if it now no longer works, or to enable it to dry out.It is generally not possible to continue using the device or associatedapparatus immediately after the ingress of liquid. This down-time, whenthe device is out of service, can be expensive in commercialenvironments and potentially life threatening if the device was beingused to control hospital equipment.

In instances where the device has not been rendered wholly inoperable bythe ingress of liquid, but has nevertheless taken in liquid, it is oftenneither possible nor recommended to wash it clean again, as the cleaningwater may itself cause further damage to the electronic components.However, cleaning may be necessary, particularly if the fouling liquidis dirty. Traditional trackballs and mice require a relatively skilledperson to clean them, which is costly in both time and money.

Ingress of solid matter (e.g. dirt and powder particles etc.) is alsodetrimental to the operation of pointing devices.

A further issue concerning optical trackballs in particular is that theoverall height of the trackball assembly has traditionally beendetermined by the height of the ball, with the overall assembly beinggreater than the height of the ball. It is highly desirable to minimisethe height of the trackball assembly, in order to enable it to beinstalled in equipment in which the available depth is limited.

It is a general object of the present invention to provide pointingdevices which overcome or at least mitigate some or all of the abovedisadvantages associated with traditional pointing devices.

According to a first aspect of the invention there is provided anelectronic pointing or cursor control device comprising a first chamberand a second chamber, wherein: the two chambers are adjoined andseparated by a fluid-tight separating wall; the first chamber containselectronic components; the second chamber comprises an aperture; thesecond chamber contains a ball, the ball protruding through saidaperture; the said separating wall comprises an optically permeableregion; and the electronic components include optical detection meansdirected towards the optically permeable region and the ball, thedetection means being operable in use to detect motion of the ball andto generate electronic signals representative of said motion.

Using two chambers separated by a fluid-tight wall provides theadvantage that the electronic components are prevented from coming intocontact with any liquid that enters the chamber containing the ball. Thedevice is therefore not susceptible to damage from the effect of liquidcoming into contact with the electronic components, and may continue tobe used with liquid in the second chamber.

The two chambers being adjoined advantageously gives rise to a compactoverall device that is relatively straightforward to manufacture.

The term “chamber” as used herein should be interpreted broadly, toencompass any volume or space in the pointing device on either side ofthe fluid-tight separating wall.

Importantly, there is no need for either chamber to be closed (i.e.bounded by walls on all sides), let alone for either chamber to befluid-tight.

The aperture through which the ball protrudes from the second chambermay be a hole or opening in a wall of the second chamber. Alternativelythe second chamber may be open-ended (i.e. the aperture is in effect theabsence of a wall altogether), in which case the pointing device may beadapted to be butted against an existing panel (e.g. in a controlconsole), and the existing panel may have a hole through which the ballmay protrude.

The term “optically permeable” should be interpreted as having theproperty of allowing optical signals to pass from the ball to thedetection means such that, in use, the detection means can correctlydetect motion of the ball.

Preferably the first chamber is fluid-tight.

Preferably the ball is mounted in the second chamber such that thedistance in the second chamber between the surface of said opticallypermeable region and the surface of the ball is sufficiently small suchthat any liquid between the ball and the optically permeable region ofthe separating wall is thinly dispersed and does not prevent opticaltransmission between the ball and the detection means.

Particularly preferably the distance in the second chamber between thesurface of said optically permeable region and the surface of the ballis less than 1.5 mm.

Preferably the detection means comprise an optical lens, the focal depthof said lens being such as to ensure that, irrespective of the nature ofany liquid between the ball and the optically permeable region of theseparating wall, the detection means are sufficiently focused to enablethe device to operate.

In preferred embodiments the separating wall may be made of atranslucent plastics material, or a clear plastics material with atextured finish. This provides the advantage of preventing users fromreadily seeing the internal components of the first chamber. Theoptically permeable region of the separating wall may comprise apolished region of the said plastics material.

Preferably the second chamber further comprises a drainage outlet. Thisadvantageously enables any liquid that has entered the second chamber todrain out.

The second chamber may further comprise a cleaning fluid inlet. Thisadvantageously enables cleaning fluid to be supplied into the secondchamber and then out through the drainage outlet, thereby keeping thesecond chamber and the ball clean without the intervention of a cleaningperson. Accordingly, the second chamber may contain a cleaning liquid.

The optical detection means may be mounted in a position substantiallyon a diametric line though the ball normal to the mounting plane of thedevice. The term “mounting plane” is used herein to refer to the planeagainst which or parallel to which the device is mounted in use. Themounting plane may be, for example, the plane of a control console inwhich the device is installed.

However, in preferred embodiments, the optical detection means aremounted at an angular position around the circumference of the ball suchthat a radial line from the ball to the detection means forms a non-zeroangle with a diametric line though the ball normal to the mounting planeof the device. Mounting the detection means in such an angular positionresults in the height of the device being reduced from what it wouldhave been were the detection means mounted on the diametric line throughthe ball. Thus, the detection means may advantageously be positioned soas to be within the profile of the ball when viewed from the side, suchthat the overall height of the device is no greater than that of theball.

In some preferred embodiments, the optical detection means are mountedat an angular position around the circumference of the ball such that aradial line from the ball to the detection means forms a non-zero angleof between 0° and 20° with a diametric line though the ball normal tothe mounting plane of the device. It has been found that, within thisrange of angles, the user's brain can compensate for any discrepancybetween ball movement and the resulting movement of the cursor, withoutthe need for the output from the detection means to be trigonometricallyprocessed.

In other preferred embodiments, the optical detection means are mountedat an angular position around the circumference of the ball such that aradial line from the ball to the detection means forms an angle ofbetween 20° and 50° with a diametric line though the ball normal to themounting plane of the device. With this range of angles, preferably thedevice further comprises processing means configured to apply vectortransformations to the signals generated by the detection means in orderto compensate for the angular position at which the detection means aremounted.

In yet further preferred embodiments, the optical detection means aremounted at an angular position around the circumference of the ball suchthat a radial line from the ball to the detection means forms an angleof substantially 90° with a diametric line though the ball normal to themounting plane of the device. Preferably the optical detection meanscomprise two optical detectors mounted in mutually orthogonal positionswith respect to said diametric line. The use of two optical detectorsarranged in orthogonal positions (effectively on the equator of theball) advantageously enables one detector to be assigned to ballmovement in one direction (e.g. the X-axis), and the other to movementin the orthogonal direction (e.g. the Y-axis). Processing of the signalsfrom the two orthogonal detectors is straightforward, and trigonometricprocessing is not required.

Preferably the device is a trackball. Alternatively it may be a mouse.

According to a second aspect of the invention there is provided anelectronic pointing or cursor control device comprising a ball andoptical detection means responsive to movement of the ball, the opticaldetection means being operable in use to detect motion of the ball andto generate electronic signals representative of said motion, whereinthe detection means are mounted at an angular position around thecircumference of the ball such that a radial line from the ball to thedetection means forms a non-zero angle with a diametric line though theball normal to the mounting plane of the device.

As mentioned above, mounting the detection means at a non-zero angleresults in the height of the device being reduced from what it wouldhave been were the detection means mounted in line with the diametricline through the ball. Thus, the detection means may advantageously bepositioned so as to be within the profile of the ball when viewed fromthe side, such that the overall height of the device is no greater thanthat of the ball.

Preferably the detection means are mounted at an angle of substantially90° from a diametric line though the ball normal to the mounting planeof the device, said angle being measured from the centre of the ball.Particularly preferably the detection means comprise two opticaldetectors mounted in mutually orthogonal positions with respect to saiddiametric line. The use of two optical detectors arranged in orthogonalpositions (effectively on the equator of the ball) advantageouslyenables one detector to be assigned to ball movement in one direction(e.g. the x-axis), and the other to movement in the orthogonal direction(e.g. the y-axis). Processing of the signals from the two orthogonaldetectors is straightforward, and trigonometric processing is notrequired.

Alternatively, preferably the detection means are mounted at a non-zeroangle of between 0° and 20° from a diametric line though the ball normalto the mounting plane of the device, said angle being measured from thecentre of the ball.

As a further alternative, preferably the detection means are mounted atan angle of between 20° and 50° from a diametric line though the ballnormal to the mounting plane of the device, said angle being measuredfrom the centre of the ball. In this case, the device may furthercomprise processing means configured to apply vector transformations tothe signals generated by the detection means in order to compensate forthe angle at which the detection means are mounted.

Preferably the device further comprises a first chamber and a secondchamber, and: the two chambers are adjoined and separated by afluid-tight separating wall; the first chamber contains electroniccomponents; the second chamber comprises an aperture; the second chambercontains the ball, the ball protruding through said aperture; the saidseparating wall comprises an optically permeable region; and theelectronic components include optical detection means directed towardsthe optically permeable region and the ball. The advantages of using twochambers separated by a fluid-tight wall have been described above.

Preferably the first chamber is fluid-tight.

Preferably the distance in the second chamber between the surface ofsaid optically permeable region and the surface of the ball issufficiently small such that any liquid between the ball and theoptically permeable region of the separating wall is thinly dispersedand does not prevent optical transmission between the ball and thedetection means. Particularly preferably the distance in the secondchamber between the surface of said optically permeable region and thesurface of the ball is less than 1.5 mm.

Preferably the detection means comprise an optical lens, the focal depthof said lens being such as to ensure that, irrespective of the nature ofany liquid between the ball and the optically permeable region of theseparating wall, the detection means are sufficiently focused to enablethe device to operate.

Preferably the separating wall is made of a translucent plasticsmaterial. Particularly preferably the optically permeable region of theseparating wall comprises a polished region of the said plasticsmaterial.

Preferably the second chamber further comprises a drainage outlet.

Preferably the second chamber further comprises a cleaning fluid inlet.

Preferably the second chamber contains cleaning liquid.

Preferably the device is a trackball. Alternatively it may be a mouse.

Embodiments of the invention will now be described, by way of example,and with reference to the drawings in which:

FIG. 1 illustrates a cross section of a trackball in accordance with thefirst aspect of the invention, incorporating two separate chambers, oneof which is fluid-tight and contains the electronic components, and theother of which contains the ball;

FIG. 2 illustrates a cross section of another trackball in accordancewith the first aspect of the invention, wherein the chamber containingthe ball has a drainage outlet, a cleaning fluid inlet, and containssome liquid therein;

FIG. 3 illustrates in cross section a mouse, also in accordance with thefirst aspect of the present invention;

FIG. 4 illustrates the geometry of a ball of a pointing device,indicating the relative positions of the device's mounting plane andpossible positions of optical sensors;

FIG. 5 illustrates a plan view (FIG. 5 a) and sectional views (FIGS. 5 band 5 c) of embodiments of a trackball in accordance with the first andsecond aspects of the invention, in which two optical sensors areequatorially mounted around the ball, and in which the sensors areseparated from the ball chamber by a fluid-tight wall;

FIG. 6 illustrates a plan view (FIG. 6 a) and a sectional view (FIG. 6b) of an embodiment of a trackball in accordance with the second aspectof the invention;

FIG. 7 illustrates a plan view (FIG. 7 a) and a sectional view (FIG. 7b) of another embodiment of a trackball in accordance with the first andsecond aspects of the invention; and

FIG. 8 illustrates a plan view (FIG. 8 a), a sectional side view (FIG. 8b), a side view (FIG. 8 c) and a sectional plan view (FIG. 8 d) of anembodiment of a mouse in accordance with the second aspect of theinvention.

DUAL-CHAMBER POINTING DEVICES

FIG. 1 illustrates an optical trackball assembly 10 comprising twochambers 15, 16 separated by a fluid-tight separating wall 17 common toboth chambers. The first chamber 15 is formed by the side walls 11, 13of the device, the base panel 12 and the separating wall 17. The sidewalls 11, 13 and the separating wall 17 may be made from a single pieceof material (e.g. a plastics moulding) which advantageously enablesmanufacturing costs to be minimised and the device to be made compact.

The first chamber 15 contains the electronic components the devicerequires for operation, principally a printed circuit board 22 and anoptical sensor 26, details of which will be given later. The firstchamber 15 is fluid-tight, thereby preventing liquid from theenvironment coming into contact with the electronic components 22, 26. Acable gland 28 is provided to enable a cable (not shown) to be connectedto the circuit board 22 whilst still maintaining a sealed chamber. Whenin use, this cable is connected to another piece of equipment such as apersonal computer or a piece of computer controlled machinery. The cablegland 28 may be located on a side wall (e.g. wall 11) of the firstchamber, as an alternative to being underneath the device.

The second chamber 16 is open to the environment, and contains the ball19 that, in use, is manipulated by a user, for example to control acursor. The second chamber is formed by the side walls 11, 13, theseparating wall 17, and the top panel 14. A chassis 20 is located withinthe second chamber 16, the chassis being adapted to support the ball 19.The top panel 14 may be removable, to enable the ball to be removed ifnecessary.

Since the first chamber 15 is separated from the second chamber 16 bythe fluid-tight separating wall 17, any liquid that enters the secondchamber from the environment cannot reach the electronic components.Indeed, a key aspect of this device is that there are no water-sensitiveelectronic components in the second chamber, and no electricalconnections run between the chambers.

The fluid-tight separating wall 17 may also be used to separateexplosive or harmful gases from the electronic components. This isparticularly useful in petrol stations, refineries, gas plants and otherinstances in which there is a danger of explosion or fire resulting fromthe ingress of flammable gases into electrical cabinets. Thus, flammablegases are safely contained in the second chamber 16, and do not reachthe electronic components in the first chamber 15.

In use, movement of the ball is detected by a solid state optical sensor26 directed towards the ball 19, and an LED (not illustrated) is used toprovide the required incident illumination on the ball. The LED ismounted in the first chamber along with all the other electroniccomponents. To enable the LED to illuminate the under-surface of theball, and to enable the sensor 26 to receive optical signals from theball, an optically permeable region 18 of sufficient size is provided inthe separating wall 17. This optically permeable region 18 may be aregion of transparent or translucent plastics material, or anothermaterial with the requisite properties as would be selected by amaterials expert.

An optical lens 24 is positioned between the sensor 26 and the opticallypermeable region 18 of the separating wall 17. (In an alternativeembodiment, the lens may be incorporated in, or integral with, theseparating wall 17.) The optical lens 24 is adapted and arranged suchthat the focal depth of the sensor 26 is sufficient to enable it todetect correctly movement of the ball, even if there is liquid in thesecond chamber.

The ball 19 is a conventional ball as used in existing optical mice andtrackballs. The surface or coated subsurface of the ball may incorporatea speckled pattern or other markings to enable the optical sensor 26 todetect the ball's motion.

Known optical mouse (or trackball) sensing technology may be employedfor all the electronic components provided to detect optically themotion of the ball. Particularly suitable for this purpose is theAgilent Technologies HDNK-2000 solid state optical mouse sensor kit.Details of the components of this kit are given in Appendix A.Alternatively the Agilent (RTM) ADNS-2051 sensor may be used in thisapplication. Future derivatives of the ADNS-2051 sensor may also be usedwith minor changes to the electronic components.

Importantly, there is only a small gap in the second chamber 16 betweenthe surface of the optically permeable region 18 of the separating wall17 and the bottom of the ball 19, as indicated by d in FIG. 1. This gapis preferably less than 1.5 mm, and is sufficiently small such that anyliquid between the ball 19 and the optically permeable region 18 of theseparating wall 17 is thinly dispersed and does not prevent opticaltransmission between the ball and the detection means.

The overall geometry of the device is such as to enable it to beretro-fitted in existing units, to replace previous trackballs.

FIG. 2 illustrates schematically a trackball assembly 30 incorporating adrainage outlet 34 and an optional cleaning fluid inlet 32. The drainageoutlet 34, which facilitates drainage of any liquid from the secondchamber 16, may be provided without the cleaning fluid inlet 32.However, advantageously, the cleaning fluid inlet 32 enables a supply ofcleaning fluid 36 to be delivered through the second chamber 16, therebykeeping the ball clean during use. As in the previous figure, the firstchamber 15 contains all the necessary electronic components for sensingmovement of the ball.

FIG. 3 illustrates an optical mouse 50 also embodying aspects of theinvention, namely two chambers 52, 54 separated by a fluid-tightseparating wall 60. The first chamber 54 is fluid-tight and includes theelectronic components including the optical sensor 58 and the switch(es)for the mouse button(s) 64. The second chamber 52 houses the ball 56 andis open to the environment. The separating wall 60 separating the firstand second chambers includes an optically permeable region 62 enablingthe optical sensor apparatus to detect motion of the ball and togenerate signals representative of that motion. Also shown in FIG. 3 areinternal electrical cables 68 which carry signals from the mousebutton(s) 64 and the optical sensor 58, a cable gland 66, and anexternal cable 70 for connection to a computer.

Reduced Height Pointing Devices

The overall height of any of the above dual-chamber devices may bereduced by moving the optical sensor around the circumference of theball to an angular position such that a radial line from the ball to thesensor forms a non-zero angle with a diametric line though the ballnormal to the mounting plane of the device. This is illustrated in FIG.4, in which the non-zero angle is indicated by α, the angular positionof the sensor is B, the said diametric line is 80 and the mounting planeof the device is 82.

It will be appreciated that an optical sensor may be positioned in suchan angular position to provide the benefits of height reduction even ifthe pointing device assembly is not formed using two chambers asdescribed above. Indeed, the principle that will now be described forconstructing reduced height (or “slim-line”) pointing devices is equallyapplicable to conventional non-fluid-tight pointing devices as well asthose described above.

In the dual-chamber pointing devices described above, the optical sensoris mounted in a position on a diametric line though the ball normal tothe mounting plane of the device. This mounting position is indicated asposition A in FIG. 4, beneath the ball on the vertical axis (Z). In use,an optical sensor in this position has the advantage that X and Yrotation in the User Coordinate System (UCS) maps directly to X and Ymovement in the Electrical Coordinate system (ECS). That is to say,movement of the ball is proportional to movement of the cursor onscreen, and no distortion of the cursor movement is apparent on screen.However, the disadvantage of this arrangement is that the overall depthof the unit is increased by having the sensor beneath the ball.

To reduce the overall height of the trackball assembly, it is desirableto position the optical sensor at a position such as B, so that theprofile of the assembly (when viewed from the side) does not extendbelow the lowest point of the ball. Thus, the overall height of thedevice is no greater than the height of the ball alone. However,mounting the sensor in a position such as B results in an unequalmapping between the UCS and ECS, and accordingly trigonometriccompensation may be required to provide direct mapping between ballmovement and X/Y cursor movement on the screen.

In practice, whether trigonometric compensation is required or notdepends on the size of the angle α (FIG. 4). There are four generalcases.

-   Case 1: α=0°: No distortion of the cursor movement on screen, so no    trigonometric compensation required.-   Case 2: 0°<α<20°: The error without compensation as seen on the    screen is at a level which may be undetectable by the human user.    Any distortion of the cursor movement on screen is intuitively    compensated by the user's brain and their hand-eye coordination.-   Case 3: 20°<α<50°: The error without compensation as seen on the    screen is at a level which is detectable by the human user and which    should be compensated trigonometrically.

This compensation is performed by a microprocessor, performing vectortransformations on the output signals from the sensors.

It should be appreciated that the angles of 20° and 50° mentioned aboveare only approximate values.

It should also be noted that the above approximations hold true when theball is moved at a reasonable speed (greater than or equal toapproximately one rotation per second). For very slow ball motion itbecomes impossible to perform the vector transformations since thepreferred protocol employed uses only integer values to denote the ballmovement.

As α approaches 90°, trigonometric solution of the error between the UCSand ECS becomes increasingly impractical with increasing a. However, inorder to obtain a trackball unit of minimal height (such that nothingextends below the lowest part of the ball), the optimal physicallocation of the optical sensor occurs at α=90°. Here, the physical depthprofile of the device is equal to the diameter of the ball (typically 50mm).

Before discussing further the special case of α=90°, it is useful toconsider first the response characteristics of an optical sensor todifferent directions of rotation of a ball. An optical sensor is notresponsive to the rotation of a ball about an axis collinear with animaginary radial line extended from the centre of the ball to thesensor. For example, if the sensor is placed directly beneath the ball(e.g. in position A), it will not detect any rotation of the ball aboutthe vertical axis Z. This is not of concern when the sensor is directlybeneath the ball, as this type of rotation would not be used to controla cursor, and the ball would ordinarily be rotated about a horizontalaxis (e.g. X or Y) instead. The corresponding direction of motion in theX/Y plane would be detected by the sensor in position A beneath theball, this being possible because the axis of rotation is not collinearwith the above-mentioned radial line from the ball to the sensor.

When α=90°, it is therefore necessary to use two optic sensorspositioned mutually orthogonally with respect to the vertical Z axis,for example at points C and D in FIG. 4. As discussed above, a singlesensor positioned in one of these positions would not be responsive tocertain conditions of ball rotation, and it would not be possible toapply mathematical compensation to a single sensor to achieve anequivalent effect. For example, the sensor in position C would beunresponsive to rotation of the ball in the Y direction, and would onlyrespond to rotation in the X direction. Likewise, the sensor in positionD would be unresponsive to rotation of the ball in the X direction, andwould only respond to rotation in the Y direction. Hence, by using twosensors in mutually orthogonal positions, both X and Y rotation can bedetected. Each sensor provides a separate X or Y component of the ECS,which may mapped directly to the UCS without the need for vectortransformations or equivalent signal processing.

FIGS. 5 to 8 illustrate examples of pointing device assemblies in whichtwo sensors are used, substantially in positions equivalent to C and Din FIG. 4.

FIGS. 5 a, 5 b and 5 c illustrate a first example of a trackballassembly having two optical sensors 100, 102 positioned orthogonallyabout the equator 104 of the ball 110. That is to say, the sensors arepositioned around the circumference of the ball such that a radial line105 from the centre of the ball to each sensor (e.g. 100) subtends thevertical diametric line 106 (which is normal to the device's mountingplane 108) at an angle of 90°.

The ball 110 (which is, for example, 50 mm in diameter) is retained inthe assembly by a removable top plate 101, secured to the assembly belowby screws 103, 105 or equivalent fixing means. A top plate to retain theball is not necessary, however, and some embodiments may be designedsuch that the ball may be lifted straight out of the assembly, e.g. tofacilitate cleaning. A bearing 107 is provided to assist the freerotation of the ball 110.

The ball 110 is in a first chamber 112 in which fluid ingress may inprinciple occur. To prevent any fluid in the first chamber from reachingthe electronic components such as the optical sensors 100, 102, eachsensor (e.g. 100) is effectively in a separate chamber 114 to thechamber 112 containing the ball, with the chambers 112 and 114 beingseparated by a fluid-tight wall 116 having an optically permeable regionto permit transmission of the optical signal.

To enable fluid to be drained from the first chamber 112, a drainageoutlet 118 may be incorporated. A cleaning fluid inlet may also beprovided, although this is not illustrated.

For applications in which fluid ingress is not a problem, but in which aslim-line pointing device is desired, a trackball assembly may beconstructed using two sensors mounted orthogonally about the equator ofthe ball, but without using two chambers. This is illustrated in FIGS. 6a and 6 b. In FIG. 6 b, one sensor 200 is shown, acting directly on theball 210. A second sensor (not shown) is mounted on the same equatoriallevel as the first sensor 200, but in an orthogonal position withrespect to the first sensor and the vertical diametric line 206.

FIGS. 7 a and 7 b illustrate a variant of the device illustrated in FIG.5. In this case, the height of the housing 301 is less than that of theball 310, so that the overall height of the assembly is no greater thanthat of the ball 310. The ball 310 is retained in the housing 301 by atop plate 303. To achieve the slim-line profile shown in FIG. 7 a, twosensors 300, 302 are equatorially mounted about the ball 310, in asimilar manner to FIG. 5. Each sensor 300, 302 is in its own chamber304, 306 respectively, to prevent fluid ingress around the ball fromreaching the electrical components.

Finally, FIGS. 8 a, 8 b, 8 c and 8 d illustrate views of a mouse 400 inwhich two optical sensors 420, 422 are equatorially mounted around theball 410 in order to achieve a slim-line assembly. With reference toFIG. 8 b, the equatorial plane of the ball is indicated by the line 424,which is normal to the diametric line 426. As with the trackballembodiments described above, this diametric line may be considered to benormal a mounting plane 428, which in this case is the plane on whichthe mouse operates when in use.

The mouse assembly also includes a housing 402 made up of a top casing404 and a bottom casing 406, and control buttons 412, 413, 414 and 415.FIGS. 8 b and 8 c show that the depth of the housing is less than theheight of the ball (which is itself only 25 mm in diameter), and thisresults in the ball protruding both above and below the housing. Becauseof this, this mouse may also be used as a hand-held trackball device.

In the embodiment shown in FIG. 8, the optical sensors 420, 422 are notseparated from the ball chamber by a fluid-tight barrier wall, althoughit will be appreciated that such a barrier could readily be incorporatedif required.

Appendix A Agilent Technologies HDNK-2000 Solid State Optical MouseSensor Kit

Kit Components

See table below.

Sensor

The sensor technical information is contained in the HDNS-2000 DataSheet and Application Note 1179.

Lens

The lens information is contained in the HDNS-2100 Data Sheet andApplication Note 1179.

LED Assembly Clip

The assembly information is contained in the HDNS-2200 Technical DataSheet and the HDNS-2000 Application Note 1179.

LED

Information on the LED is contained in the HLMP-ED80 Data Sheet andApplication Note 1179.

Base Plate Feature IGES File

The IGES file provides recommended base plate moulding features toensure optical alignment.

Part Number Description Name HDNS-2000 Solid state optical mouse sensorSensor HDNS-2100 Lens plate Lens HDNS-2200 LED Assembly Clip LED ClipHLMP-ED80 639 nm T 1¾ (5 mm) diameter LED LED Documentation HDNS-2000Data Sheet — Documentation HDNS-2100 Data Sheet — DocumentationHDNS-2200 Data Sheet — Documentation LED Data Sheet — DocumentationApplication Note 1179 — Floppy Diskette Base Plate Feature IGES File —

The address of Agilent Technologies, Inc. is 395 Page Mill Road, PaloAlto, Calif. 94303, United States of America.

1. An electronic pointing or cursor control device comprising a firstchamber and a second chamber, wherein: the first chamber is fluid tight;the two chambers are adjoined and separated by a fluid-tight separatingwall; the first chamber contains electronic components; the secondchamber comprises an aperture; the second chamber contains a ball, theball protruding through said aperture; the said separating wallcomprises an optically permeable region; and the electronic componentsinclude an optical detector directed towards the optically permeableregion and the ball, the optical detector being operable in use todetect motion of the ball and to generate electronic signalsrepresentative of said motion, wherein the distance in the secondchamber between the surface of said optically permeable region and thesurface of the ball is sufficiently small such that any liquid betweenthe ball and the optically permeable region of the separating wall isthinly dispersed and does not prevent optical transmission between theball and the optical detector.
 2. A device as claimed in claim 1,wherein the distance in the second chamber between the surface of saidoptically permeable region and the surface of the ball is less than 1.5mm.
 3. A device as claimed in claim 1, wherein the optical detectorcomprises an optical lens, the focal depth of said lens being such as toensure that, irrespective of the nature of any liquid between the balland the optically permeable region of the separating wall, the opticaldetector is sufficiently focused to enable the device to operate.
 4. Adevice as claimed in claim 1, wherein the separating wall is made of atranslucent plastics material.
 5. A device as claimed in claim 4,wherein the optically permeable region of the separating wall comprisesa polished region of the said plastics material.
 6. A device as claimedin claim 1, wherein the second chamber further comprises a drainageoutlet.
 7. An electronic pointing or cursor control device comprising afirst chamber and a second chamber, wherein: the two chambers areadjoined and separated by a fluid-tight separating wall; the firstchamber contains electronic components; the second chamber comprises anaperture; the second chamber contains a ball, the ball protrudingthrough said aperture; the said separating wall comprises an opticallypermeable region; the electronic components include an optical detectordirected towards the optically permeable region and the ball, theoptical detector being operable in use to detect motion of the ball andto generate electronic signals representative of said motion; the secondchamber further comprises a drainage outlet; and the second chamberfurther comprises a cleaning fluid inlet.
 8. A device as claimed inclaim 1, wherein the second chamber contains cleaning liquid.
 9. Adevice as claimed in claim 1, wherein the optical detector is mounted ina position substantially on a diametric line through the ball normal tothe mounting plane of the device.
 10. A device as claimed in claim 1,wherein the optical detector is mounted at an angular position aroundthe circumference of the ball such that a radial line from the ball tothe optical detector forms a non-zero angle with a diametric linethrough the ball normal to the mounting plane of the device.
 11. Adevice as claimed in claim 10, wherein the optical detector is mountedat an angular position around the circumference of the ball such that aradial line from the ball to he optical detector forms a non-zero angleof between 0° and 20° with a diametric line through the ball normal tothe mounting plane of the device.
 12. A device as claimed in claim 10,wherein the optical detector is mounted at an angular position aroundthe circumference of the ball such that a radial line from the ball tothe optical detector forms a non-zero angle of between 20° and 50° witha diametric line through the ball normal to the mounting plane of thedevice.
 13. A device as claimed in claim 12, further comprising aprocessor configured to apply vector transformations to the signalsgenerated by the optical detector in order to compensate for the angularposition at which the optical detector is mounted.
 14. A device asclaimed in claim 10, wherein the optical detector is mounted at anangular position around the circumference of the ball such that a radialline from the ball to the optical detector forms an angle ofsubstantially 90° with a diametric line through the ball normal to themounting plane of the device.
 15. A device as claimed in claim 14,wherein the optical detector is one of two such optical detectorsmounted in mutually orthogonal positions with respect to said diametricline.
 16. A device as claimed in claim 1 being a trackball.
 17. A deviceas claimed in claim 1 being a mouse.